Depending on more and more popular computers, the data saved in the computers by people is increasingly huge, so that computer manufacturers must be continuously engaged in development of larger-capacity storage media. However, the large-capacity storage media such as hard drives are generally limited on data transmission rate due to their reading heads with accessing rate and the transmission rate of the bus connecting thereto. In addition, once the storage media that have no error-tolerance function are destroyed, the stored data will also be destroyed.
Accordingly, the redundant array of inexpensive disks (RAID) is developed, which is a virtual logic hard drive stimulated by several physical hard drives. The RAID array can simultaneously access data from several physical hard drives, so that the virtual logic hard drive has a faster data transmission rate. Besides, some RAID arrays have error-tolerance function, when one of the physical hard drives of the RAID array is broken, the data in the broken physical hard drive can be recovered from the other physical hard drives.
For replacing the physical hard drives of the RAID array at any time, the hot-plug physical hard drive is essential to RAID array. However, when software is applied to emulate RAID array, it is necessary to monitor and to deal with plug in or out of the physical hard drive under the circumstance with RAID drivers at any time.